Set the playbooks explicitly bound to a space type

Declaratively sets which playbooks are explicitly bound to the space type named in the path. Body: { playbookIds: string[] } — the desired full set of explicitly-bound playbook ids. Each changed playbook has this space type added to / removed from its spaceTypes array; unchanged playbooks are not touched. Playbooks with an EMPTY spaceTypes apply to all space types and are ignored by this endpoint — listing their id has no effect (binding one explicitly would silently restrict it everywhere else). Authorization: organization administrators only — other callers get 403. Returns 404 not_found if the space type does not exist; 400 unknown_playbook if an id matches no playbook. Response: the same annotated list as GET, after the update.